Add Uninitialized variant to Renderer (#608)

* Add Uninitialized variant to Renderer

Thereby we don't need to panic when PaintState is uninitialized.

* Remove now redundant is_initialized check

* Make Renderer own the size

* Add some doc comments

* Improve wording

src/app_handle.rs

@@ -137,12 +137,6 @@ impl ApplicationHandle {
             None => return,
         };
 
-        // We only start reacting to events once the window is ready
-        // I.e. once the renderer has acquired the necessary GPU resources (if any) and is initialized.
-        if !window_handle.is_initialized() {
-            return;
-        }
-
         let start = window_handle.profile.is_some().then(|| {
             let name = match event {
                 WindowEvent::ActivationTokenDone { .. } => "ActivationTokenDone",

src/context.rs

@@ -16,6 +16,7 @@ use web_time::{Duration, Instant};
 use taffy::prelude::NodeId;
 
 use crate::animate::{AnimStateKind, RepeatMode};
+use crate::renderer::Renderer;
 use crate::style::DisplayProp;
 use crate::view_state::IsHiddenState;
 use crate::{
@@ -1194,13 +1195,20 @@ impl<'a> PaintCx<'a> {
 
 // TODO: should this be private?
 pub enum PaintState {
+    /// The renderer is not yet initialized. This state is used to wait for the GPU resources to be acquired.
     PendingGpuResources {
         window: Arc<dyn wgpu::WindowHandle>,
         rx: crossbeam::channel::Receiver<Result<GpuResources, GpuResourceError>>,
-        scale: f64,
-        size: Size,
         font_embolden: f32,
+        /// This field holds an instance of `Renderer::Uninitialized` until the GPU resources are acquired,
+        /// which will be returned in `PaintState::renderer` and `PaintState::renderer_mut`.
+        /// All calls to renderer methods will be no-ops until the renderer is initialized.
+        ///
+        /// Previously, `PaintState::renderer` and `PaintState::renderer_mut` would panic if called when the renderer was uninitialized.
+        /// However, this turned out to be hard to handle properly and led to panics, especially since the rest of the application code can't control when the renderer is initialized.
+        renderer: crate::renderer::Renderer<Arc<dyn wgpu::WindowHandle>>,
     },
+    /// The renderer is initialized and ready to paint.
     Initialized {
         renderer: crate::renderer::Renderer<Arc<dyn wgpu::WindowHandle>>,
     },
@@ -1216,28 +1224,26 @@ impl PaintState {
     ) -> Self {
         Self::PendingGpuResources {
             window,
-            scale,
-            size,
             rx,
             font_embolden,
+            renderer: Renderer::Uninitialized { scale, size },
         }
     }
 
     pub(crate) fn init_renderer(&mut self) {
         if let PaintState::PendingGpuResources {
             window,
             rx,
-            scale,
-            size,
             font_embolden,
+            renderer,
         } = self
         {
             let gpu_resources = rx.recv().unwrap().unwrap();
             let renderer = crate::renderer::Renderer::new(
                 window.clone(),
                 gpu_resources,
-                *scale,
-                *size,
+                renderer.scale(),
+                renderer.size(),
                 *font_embolden,
             );
             *self = PaintState::Initialized { renderer };
@@ -1248,9 +1254,7 @@ impl PaintState {
 
     pub(crate) fn renderer(&self) -> &crate::renderer::Renderer<Arc<dyn wgpu::WindowHandle>> {
         match self {
-            PaintState::PendingGpuResources { .. } => {
-                panic!("Tried to access renderer before it was initialized")
-            }
+            PaintState::PendingGpuResources { renderer, .. } => renderer,
             PaintState::Initialized { renderer } => renderer,
         }
     }
@@ -1259,9 +1263,7 @@ impl PaintState {
         &mut self,
     ) -> &mut crate::renderer::Renderer<Arc<dyn wgpu::WindowHandle>> {
         match self {
-            PaintState::PendingGpuResources { .. } => {
-                panic!("Tried to access renderer before it was initialized")
-            }
+            PaintState::PendingGpuResources { renderer, .. } => renderer,
             PaintState::Initialized { renderer } => renderer,
         }
     }

src/renderer.rs

@@ -60,6 +60,12 @@ use peniko::BrushRef;
 pub enum Renderer<W> {
     Vger(VgerRenderer),
     TinySkia(TinySkiaRenderer<W>),
+    /// Uninitialized renderer, used to allow the renderer to be created lazily
+    /// All operations on this renderer are no-ops
+    Uninitialized {
+        scale: f64,
+        size: Size,
+    },
 }
 
 impl<W: wgpu::WindowHandle> Renderer<W> {
@@ -118,20 +124,35 @@ impl<W: wgpu::WindowHandle> Renderer<W> {
         match self {
             Renderer::Vger(r) => r.resize(size.width as u32, size.height as u32, scale),
             Renderer::TinySkia(r) => r.resize(size.width as u32, size.height as u32, scale),
+            Renderer::Uninitialized { .. } => {}
         }
     }
 
     pub fn set_scale(&mut self, scale: f64) {
         match self {
             Renderer::Vger(r) => r.set_scale(scale),
             Renderer::TinySkia(r) => r.set_scale(scale),
+            Renderer::Uninitialized {
+                scale: old_scale, ..
+            } => {
+                *old_scale = scale;
+            }
         }
     }
 
     pub fn scale(&self) -> f64 {
         match self {
             Renderer::Vger(r) => r.scale(),
             Renderer::TinySkia(r) => r.scale(),
+            Renderer::Uninitialized { scale, .. } => *scale,
+        }
+    }
+
+    pub fn size(&self) -> Size {
+        match self {
+            Renderer::Vger(r) => r.size(),
+            Renderer::TinySkia(r) => r.size(),
+            Renderer::Uninitialized { size, .. } => *size,
         }
     }
 }
@@ -145,6 +166,7 @@ impl<W: wgpu::WindowHandle> floem_renderer::Renderer for Renderer<W> {
             Renderer::TinySkia(r) => {
                 r.begin(capture);
             }
+            Renderer::Uninitialized { .. } => {}
         }
     }
 
@@ -156,6 +178,7 @@ impl<W: wgpu::WindowHandle> floem_renderer::Renderer for Renderer<W> {
             Renderer::TinySkia(v) => {
                 v.clip(shape);
             }
+            Renderer::Uninitialized { .. } => {}
         }
     }
 
@@ -167,6 +190,7 @@ impl<W: wgpu::WindowHandle> floem_renderer::Renderer for Renderer<W> {
             Renderer::TinySkia(v) => {
                 v.clear_clip();
             }
+            Renderer::Uninitialized { .. } => {}
         }
     }
 
@@ -178,6 +202,7 @@ impl<W: wgpu::WindowHandle> floem_renderer::Renderer for Renderer<W> {
             Renderer::TinySkia(v) => {
                 v.stroke(shape, brush, width);
             }
+            Renderer::Uninitialized { .. } => {}
         }
     }
 
@@ -194,6 +219,7 @@ impl<W: wgpu::WindowHandle> floem_renderer::Renderer for Renderer<W> {
             Renderer::TinySkia(v) => {
                 v.fill(path, brush, blur_radius);
             }
+            Renderer::Uninitialized { .. } => {}
         }
     }
 
@@ -205,6 +231,7 @@ impl<W: wgpu::WindowHandle> floem_renderer::Renderer for Renderer<W> {
             Renderer::TinySkia(v) => {
                 v.draw_text(layout, pos);
             }
+            Renderer::Uninitialized { .. } => {}
         }
     }
 
@@ -216,6 +243,7 @@ impl<W: wgpu::WindowHandle> floem_renderer::Renderer for Renderer<W> {
             Renderer::TinySkia(v) => {
                 v.draw_img(img, rect);
             }
+            Renderer::Uninitialized { .. } => {}
         }
     }
 
@@ -232,6 +260,7 @@ impl<W: wgpu::WindowHandle> floem_renderer::Renderer for Renderer<W> {
             Renderer::TinySkia(v) => {
                 v.draw_svg(svg, rect, brush);
             }
+            Renderer::Uninitialized { .. } => {}
         }
     }
 
@@ -243,6 +272,7 @@ impl<W: wgpu::WindowHandle> floem_renderer::Renderer for Renderer<W> {
             Renderer::TinySkia(v) => {
                 v.transform(transform);
             }
+            Renderer::Uninitialized { .. } => {}
         }
     }
 
@@ -254,13 +284,15 @@ impl<W: wgpu::WindowHandle> floem_renderer::Renderer for Renderer<W> {
             Renderer::TinySkia(v) => {
                 v.set_z_index(z_index);
             }
+            Renderer::Uninitialized { .. } => {}
         }
     }
 
     fn finish(&mut self) -> Option<DynamicImage> {
         match self {
             Renderer::Vger(r) => r.finish(),
             Renderer::TinySkia(r) => r.finish(),
+            Renderer::Uninitialized { .. } => None,
         }
     }
 }

src/window_handle.rs

@@ -192,10 +192,6 @@ impl WindowHandle {
         self.render_frame();
     }
 
-    pub(crate) fn is_initialized(&self) -> bool {
-        matches!(self.paint_state, PaintState::Initialized { .. })
-    }
-
     pub fn event(&mut self, event: Event) {
         set_current_view(self.id);
         let event = event.scale(self.app_state.scale);

tiny_skia/src/lib.rs

@@ -8,7 +8,7 @@ use floem_renderer::tiny_skia::{
 use floem_renderer::Img;
 use floem_renderer::Renderer;
 use image::DynamicImage;
-use peniko::kurbo::PathEl;
+use peniko::kurbo::{PathEl, Size};
 use peniko::{
     kurbo::{Affine, Point, Rect, Shape},
     BrushRef, Color, GradientKind,
@@ -115,6 +115,10 @@ impl<W: raw_window_handle::HasWindowHandle + raw_window_handle::HasDisplayHandle
     pub fn scale(&self) -> f64 {
         self.scale
     }
+
+    pub fn size(&self) -> Size {
+        Size::new(self.pixmap.width() as f64, self.pixmap.height() as f64)
+    }
 }
 
 fn to_color(color: Color) -> tiny_skia::Color {

vger/src/lib.rs

@@ -9,6 +9,7 @@ use floem_renderer::text::{CacheKey, TextLayout};
 use floem_renderer::{tiny_skia, Img, Renderer};
 use floem_vger_rs::{Image, PaintIndex, PixelFormat, Vger};
 use image::{DynamicImage, EncodableLayout, RgbaImage};
+use peniko::kurbo::Size;
 use peniko::{
     kurbo::{Affine, Point, Rect, Shape},
     BrushRef, Color, GradientKind,
@@ -117,6 +118,10 @@ impl VgerRenderer {
     pub fn scale(&self) -> f64 {
         self.scale
     }
+
+    pub fn size(&self) -> Size {
+        Size::new(self.config.width as f64, self.config.height as f64)
+    }
 }
 
 impl VgerRenderer {